# Worker In a Juju deployment, a **worker** is a process that a Juju [agent](https://documentation.ubuntu.com/juju/2.9/reference/agent.md#agent) runs in the background on a Juju entity ([controller](https://documentation.ubuntu.com/juju/2.9/reference/controller.md#controller), [model](https://documentation.ubuntu.com/juju/2.9/reference/model.md#model), [machine](https://documentation.ubuntu.com/juju/2.9/reference/machine.md#machine), [unit](https://documentation.ubuntu.com/juju/2.9/reference/unit.md#unit), etc.) and which has responsibilities related to that entity.